8th Meeting of the ITPA Confinement Database & Modeling Topical Group on 2004.4.20 at Kyto university H-mode power threshold in JFT-2M during 2000-2004 with ferritic wall and boron coating K. Tsuzuki JAERI
Contents Modification of JFT-2M High recycling steady H-mode Installation of ferritic steel Boron coating High recycling steady H-mode Threshold power for L-H transition Effect of ferromagnetism and boron BT dependence Summary
Modification of JFT-2M(1) Installation of ferritic steel Reduced activation ferritic steel is a leading candidate for structure material of DEMO reactor but ferromagnetic and easily oxidized. Compatibility with high performance plasma is a critical issue. Ferritic steel wall Compatibility has been investigated in JFT-2M by installing ferritic wall inside vacuum vessel Graphite tiles
Possible Magnetic effect of the ferritic wall Ripple reduction Ripple amplitude at plasma periphery 2.2% -->0.4% for optimum case (2) Complex field Higher harmonics is produced (3) Error field Miss-alignment and/or inhomogeneous installation (4) Wall stabilization
Modification of JFT-2M(2) boron coating Boron coating with B(CH3)3 was first applied on JFT-2M in 2000. Oxygen impurity : reduced Hydrogen recycling : strong pumping and fueling according to wall condition
High Recycling Steady (HRS) H-mode New H-mode was found after boronization Enhancement of Da Steady H-mode edge ne/nGW > 0.4
Threshold power with/without ferritic wall Pth was compared for standard configuration BT = 1.3 T, Ip = 200 kA, q95 = 3.0 Partial ferritic full ferritic wo boron 690 kW 680 kW with boron 440 kW 420 kW Ferritic steel : No effect Boron coating : Improvement
BT dependence of Pth BT dependence of Pth was not well investigated in JFT-2M Effect of the ferritic steel change Permeability : 2 (2T) ~ 4 (0.8T) Ripple : 1.5% (0.85T) ~ 0.5% (1.3 T) JFT-2M
Other parameters BT was scanned from 0.85T to 1.9T Ip is almost constant at 200 kA q95 varied from 2 to 4.2 Low recycling conditions; not HRS but ELMy H-mode
BT dependence of Pth Pth obeys scaling law by 15 % for 0.85T < BT < 1.9T J. Snipes, ITER H-mode Threshold Database Working Group, 7th H-mode Workshop, Oxford, 1999 2.84M-1*Bt0.82*n200.58*R*a0.81
Summary Threshold power (Pth) for L-H transition has been investigated in JFT-2M after installation of ferritic steel and boron coating. Pth is not changed by the installation of ferritic wall Boron coating reduced Pth by ~250W Toroidal field was scanned for wider range than previous data sets. Ripple amplitude is also scanned from 0.4 % to 1.5 % Permeability is also scanned from 2 to 4 Pth obeys conventional scaling law (B0.82) by 15 %